The present invention relates to an oil-dissolved-gas measuring device for measuring a concentration of a flammable gas dissolved in an insulating oil for use in an oil-immersed electrical appliance.
In oil-immersed electrical appliances such as a transformer, a capacitor, a reactor and so on, it is a well-known fact that an insulating oil and a solid insulating matter are decomposed with local heat or due to an abnormal state where corona discharge locally takes place, thereby evolving a flammable gas. It is therefore possible to detect the abnormality of the oil-immersed electrical appliance before encountering an accident by detecting the flammable gas.
According to the prior art, for maintenance of the oil-immersed electrical appliances there has heretofore been adopted a method of analyzing the gas dissolved in the insulating oil, i.e., the flammable gas such as hydrogen, methane and ethylene. In such a case, the insulating oil is sampled on the spot where the oil-immersed appliance is installed, and the sampled insulating oil (hereinafter referred to as "a sample oil") is brought back to a place at which an analyzer for analyzing the sample oil is disposed.
Prior to the analysis, the dissolved gas is extracted from the sample oil by Torricellian method, Toepler pump method or stripping method. The extracted dissolved gas is analyzed by a gas chromatography, and on the basis of the result of this analysis there is made a judgment as to whether the abnormal state appears or not. This is an example of the conventional method.
In the above-described conventional method, however, a good deal of time has to be spent until the analytic result is obtained through such processes as the sampling of sample oil, the extraction of dissolved gas and the analysis by the gas chromatography. Besides, an inert gas is required as a carrier gas because of employing the gas chromatography in such a method.
In addition, the apparatus for extracting the dissolved gas and the gas chromatography suited to analyze the gas employed in the above-mentioned method have large size and high cost.